This invention relates to an accelerating device for an internal combustion engine and more particularly to an improved accelerating device for the charge forming system of an engine such as a carburetor.
As is well known with the internal combustion engines in which the fuel is introduced into the induction system of the engine rather than directly into the combustion chamber, the fuel/air ratio can deteriorate during sudden accelerations. As is well known, this leaning of the fuel/air mixture under accelerations is caused by the slower acceleration in the fuel flow than that of the air flow due to the greater density of the fuel. In order to provide smoother acceleration and the necessary enrichment, a wide variety of acceleration devices have been incorporated for adding fuel to the air flowing to the engine under extreme acceleration conditions.
One form of accelerating enrichment device employs a pumping chamber into which a fluid is drawn when the induction system vacuum is high, as it is under idle or steady state low speed operation. To accomplish this, a moveable wall separates a pumping chamber into which the fluid is drawn from a pressure sensing chamber that is in communication with the engine induction system. When the induction system pressure rises, indicating a rapid acceleration, the moveable wall is moved in a direction to force the fluid which has been drawn into the pumping chamber into the induction system for enrichment purposes.
A disadvantage of this type of accelerating enrichment device is that the pressure sensing chamber will be subjected to varying pressures and this can cause the moveable wall to move and reduce the volume of fluid pumped. These pressure variations are caused due to a wide variety of reasons, such as the fact that the induction system pressure may vary due to the fact that one or more engine chambers are supplied by the induction system and the pulsations in pressure flow can cause such variations.
To avoid these problems, it has been proposed to provide a second pressure sensing chamber that communicates with the first pressure sensing chamber through a check valve so as to isolate the first pressure sensing chamber from fluctuations in pressure in the second pressure sensing chamber. However, because of the provision of the check valve, it is necessary to provide a further passage communicating the second pressure sensing chamber with the first pressure sensing chamber so as to effect movement of the wall when the induction system pressure rises significantly to indicate the necessity for the introduction of acceleration fuel. However, this communicating passageway must be made relatively small so as to avoid movement of the wall under the aforenoted pressure variations. This causes the pumping operation to be somewhat diminished since the increased pressure in the induction system is not rapidly transmitted to the first pressure sensing chamber and hence the performance of the accelerating device may be deteriorated.
It is, therefore, an object of this invention to provide an improved accelerating device for an internal combustion engine in which the accelerating fuel supply is dampened from pressure variations in the induction system but also wherein the amount of accelerating fuel can be rapidly transmitted when called for.
It is a further object of this invention to provide an improved accelerating fuel device for an internal combustion engine induction system wherein pressure variations in the induction system will not adversely affect the output of the device but wherein the device can also rapidly supply accelerating fuel when called for.